Phacoemulsification is a well-known process that refers to the use of a phacoemulsification machine that generates ultrasonic sound waves at the tip of a handpiece. phacoemulsification machines are particularly useful in cataract surgery, for example, where it is necessary to remove a cataract lens from an eye. The tip is placed into the eye and specifically against the lens or cataract of the eye where the ultrasonic energy emulsifies the lens. The tip is hollow and emulsified pieces of the cataract are aspirated into an aspiration port formed at an end of the tip for removal from the eye. The aspirated cataract material flows through the tip, through channels within the handpiece and into an aspiration line connected to the phacoemulsification machine while fluid flows into the eye through an infusion line and an infusion sleeve formed around the tip to maintain the eye's pressure and shape.
Aspiration is driven by pumps housed within the phacoemulsification machine and infusion is typically generated by gravity. The fluid infused into the eye through the infusion sleeve also serves to suspend particles of lenticular debris within the infused fluid and the suspension is then aspirated through the aspiration line back to the phacoemulsification machine where it is collected in a receptacle. The flow created in the aspiration line generates a vacuum or negative pressure in the aspiration line and at the handpiece tip. The vacuum holds the lens material against the aspiration port of the tip where the material is emulsified.
The stronger the vacuum force is that holds the material against the aspiration port, i.e., “holdability”, the more efficient emulsification becomes. Additionally, increasing holdability allows the surgeon to manipulate lens material within the handpiece tip more easily. Holdability increases with vacuum level and aspiration port size. Therefore, higher vacuum levels and larger aspiration ports lead to more efficient phacoemulsification. However, these parameters also risk sudden collapse of the anterior chamber of the eye as fluid rapidly rushes into the aspiration port due to the large aspiration port area and the high vacuum.
For example, during aspiration of the lenticular debris, the handpiece tip often becomes occluded with this debris. When it does, the vacuum level within the aspiration line builds to a high level. Eventually, the ultrasonic sound waves at the tip emulsify the debris, freeing the occlusion at the tip and resulting in an “occlusion break”. Fluid then rapidly rushes into the aspiration port and aspiration line to satisfy the high vacuum built up in the tip and the aspiration line. This can create negative pressure in the anterior chamber relative to the posterior segment of the eye. When this occurs, the anterior chamber can collapse or the posterior capsule can shift anteriorly, both being undesirable during intraocular surgery, perhaps resulting in complications such as posterior capsule rupture.
To reduce the potential surge inflow of fluid in the aspiration line resulting from an occlusion break at the tip, emulsification tips have been manufactured in the past with a narrow lumen within the shaft of the tip that allows the surgeon to increase vacuum levels while limiting the sudden inflow of fluid in the aspiration line following an occlusion break. However, in these tip designs, the narrow portion of the lumen often becomes occluded with debris resulting in a complete loss of negative pressure or holdability at the aspiration port of the tip. The occlusion can be broken by refluxing fluid, prolonged application of ultrasonic energy or sometimes by increasing the vacuum level in the aspiration line. However, these techniques either increase the risk of complications, such as thermal injury to ocular tissues, or decrease efficiency of the emulsification surgical procedure. Additionally, these tip designs tend to have thinner walls than standard tips and are relatively fragile and more prone to breakage.
Thus, there is a need for a phacoemulsification system that reduces the danger of sudden post occlusion surge inflow of fluid within the aspiration line following an occlusion break. There is also a need for a phacoemulsification system that minimizes occlusions at the narrow lumen that can lead to a complete loss of holdability at the handpiece tip. There is yet another need for a phacoemulsification machine that improves holdability of the handpiece tip while minimizing breakage of the tip. There is still also a need for a phacoemulsification system that minimizes the risk of injury to the human eye during a phacoemulsification surgical procedure.